- Motivation - New measurements of IGM Lyα Opacity & - Implications for Reionization & High-z Galaxies with Jamie Bolton (Nottingham)

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1 Galaxy Evolution in the Reionization Era Probed Using the UV Background - Motivation - New measurements of IGM Lyα Opacity & Temperature - UVB Results George Becker Cambridge IoA & KICC GalEvol Implications for Reionization & High-z Galaxies with Jamie Bolton (Nottingham) Becker & Bolton 2013, MNRAS, in press (arxiv: )

2 The photon problem To reionize hydrogen, need to emit 3 ionizing photons/atom into the IGM by z=6 McLure BPASS Eldridge et al J / 0 For standard SEDs and 10% escape fraction, z=6 galaxies emit ~1-3 ionizing photon/atom/gyr -- but global SFR drops rapidly at z > 6! J / Myr Z = 0.2 Zsun

3 Evolving? escape fraction Ly C At z~1, fesc ~ 0 Siana Possibly higher at z~3, but difficult to measure (faintness & contamination) Nestor+ 2011, 2012 Vanzella Extremely difficult to measure at z 4

4 Ionizing Emissivity Galaxy UV Luminosity Fn SED Escape fraction + + LyC Observed UV LyC Emissivity Ṅ ion photons s -1 Mpc -3

5 Ionizing Emissivity Galaxy UV Luminosity Fn SED Escape fraction + + LyC Observed UV LyC IGM Properties Opacity Temperature H I Ionization rate + IGM opacity Emissivity Ṅ ion s-1 photons s -1 Mpc -3

6 Counting photons in the IGM z~3.5 30% lower fhi

7 Counting photons in the IGM z~3.5 / ( bh 2 ) 2 (1 + z) 6 T 0.7 H(z) (z) 30% lower fhi

8 Counting photons in the IGM z~3.5 / ( bh 2 ) 2 (1 + z) 6 T 0.7 H(z) (z) 30% lower fhi H I ionization rate s -1

9 Counting photons in the IGM z~3.5 / ( bh 2 ) 2 (1 + z) 6 T 0.7 H(z) (z) 30% lower fhi Recombination rate: B / T 0.7 H I ionization rate s -1

10 Counting photons in the IGM ) ( )( ) z~3.5 / ( bh 2 ) 2 (1 + z) 6 T 0.7 H(z) (z) 30% lower fhi Recombination Bolton rate: (see also B Miralda-Escude / T , Kuhlen & Faucher-Giguere H I ionization 2012) rate s -1

11 Lyα Opacity from Composite Spectra Avoids continuum fitting Composites of SDSS Spectra Becker+ 2013

12 Lyα Opacity from Composite Spectra Avoids continuum fitting Composites of SDSS Spectra Flux ratio = F(z1)/F(z2) Becker+ 2013

13 Lyα Opacity Results e = ln hf i 1. Much smaller errors 2. Extends to z=5 3. No bump Becker+ 2013

14 Temperatures from the Curvature Temperature-density relation: T ( )=T 0 h i 1 * Extended He II Reionization * Becker+ 2011

15 Temperatures from the Curvature Rudie Temperature-density relation: T ( )=T 0 h i 1 * Extended He II Reionization * Becker+ 2011

16 Temperatures from the Curvature Rudie Temperature-density relation: T ( )=T 0 h i 1 Bolton, Becker+ (2013) * Extended He II Reionization * Becker+ 2011

17 Hydrogen Ionization Rate log / (10 12 s 1 ) This work ( =1.40) z This work ( =1.3) Bolton & Haehnelt (2005,2007) z This work ( =1.6) Faucher Giguere et al (2008) z Becker & Bolton (2013) Ionization timescale = 1 / Γ ~ 40,000 years

18 Ionization Rate Ionizing Emissivity Roughly, N ion / HI mfp but exact treatment needed at z~2-3!

19 Ionization Rate Ionizing Emissivity Roughly, N ion / HI mfp but exact treatment needed at z~2-3! Radiative transfer: J( 0,z 0 )= 1 4 Z 1 z 0 dz dl dz (1 + z 0 ) 3 (1 + z) 3 (,z)e eff ( 0,z 0,z) Intensity Emissivity Ionizing opacity: e ( 0,z 0,z)= Z z z 0 dz 0 Z 1 0 dn HI f(n HI,z 0 )(1 e )

20 Ionizing Opacity Mean free path at 912 Å Number density of LLSs 912 (proper Mpc) 100 Prochaska O Meara Fumagalli Worseck+ in prep n LLS 10 Songaila & Cowie 2010 (includes Peroux+ 2003) z z Fit simultaneously: f(n H,I,z) / N HI N (1 + z) z N =1.32 ± 0.05 z =2.1 ± 0.3

21 Emissivity Results log N ion / (10 51 s 1 Mpc 3 ) Text x6 1 Photons/atom/Gyr 1.5 This work ( =1.3, =3.0) Bolton & Haehnelt (2007) This work ( =1.6, =3.0) Kuhlen & Faucher Giguere (2012) z z Higher values due to (1) Higher Γ (2) higher ionizing opacity (3) inclusion of radiative transfer Becker & Bolton, in prep

22 Separating AGN and Stars 2.5 log 912 / (10 23 erg s 1 Mpc 3 Hz 1 ) Total AGN: Cowie et al (2009) Galaxies dominate the emissivity near 1 Ryd at z > 4, and possibly at z > 2.4 Galaxies (Total Cowie et al AGN) 0.0 AGN: Haardt & Madau (2012) z Becker & Bolton (2013)

23 Separating AGN and Stars 2.5 log 912 / (10 23 erg s 1 Mpc 3 Hz 1 ) Total AGN: Cowie et al (2009) LBG+LAE emissivity, based on Nestor Galaxies dominate the emissivity near 1 Ryd at z > 4, and possibly at z > 2.4 Galaxies (Total Cowie et al AGN) 0.0 AGN: Haardt & Madau (2012) z Becker & Bolton (2013)

24 Ionizing efficiency of galaxies We know: 1. The ionizing emissivity from the IGM 2. The non-ionizing emissivity galaxy surveys Reddy & Steidel 2009 Ionizing UV Non-ionizing UV Compute the ionizing efficiency of galaxies...

25 Ionizing efficiency of galaxies 0.10 Galaxy UV emissivity: ionizing / non-ionizing 912 / z 1. Ionizing efficiency increases with redshift 2. Trend necessary for reionization continues to z~3 Becker & Bolton (2013)

26 Ionizing efficiency of galaxies Lyα fraction -- See R. Ellis talk 0.10 Galaxy UV emissivity: ionizing / non-ionizing 912 / Stark z = 1. Ionizing efficiency increases with redshift 2. Trend necessary for reionization continues to z~3 Becker & Bolton (2013)

27 Summary UVB reflects trends in galaxy evolution near reionization New UVB results based on new measurements of IGM properties over 2 < z < 5 - Opacity to Lyα photons - Temperature - Opacity to ionizing photons Emissivity 2-6x higher than previous estimates - Flat or increasing with redshift - More photons near the end of reionization Ionizing efficiency of galaxies increases from z~3 to z~5 The evolution in ionizing efficiency required for galaxies to reionize the IGM by z=6 continues well into the postreionization epoch.